DE102012100075A1 - Container, such as polyethylene terephthalate bottle, has recess or interruption that is designed such that one or multiple threaded bars possess two recess or interruption limiting flank surfaces at side facing recess - Google Patents

Abstract

The container has a hollow cylindrical neck section (31) with outer thread for receiving a closure cap. A recess or an interruption is designed such that one or multiple threaded bars (33,33',34,34') possess two recess or interruption limiting flank surfaces (37,38,39,40) at a side facing the recess. The two flank surfaces enclose an opening angle which is greater than 120 degrees. The opening angle is greater than 150 degrees and smaller than 225 degrees, particularly less than 190 degrees. The recesses or interruptions of the threaded bars are aligned in a thread axis direction. An independent claim is included for a multi-part mold for injection molding for the production of a container.

Description

The present invention relates to a container with a hollow cylindrical neck portion with external thread for receiving a closure cap. Furthermore, the present invention relates to a multi-part mold for producing such a container.

Such containers are often produced by injection molding. In injection molding, the material is plasticized and then injected under high pressure into an injection mold. The material remains in the mold until it changes to a solid, demoldable state. For this purpose, the molding tool forms a substantially closed space, the contour of which corresponds to the intended outer contour of the casting to be produced.

In the production of PET bottles corresponding hollow body moldings are first produced by injection molding, which are inflated in a further process step in the final bottle shape. The hollow body moldings for PET bottles produced by means of injection molding are also referred to as preforms or preforms. These hollow body moldings are containers in the context of the present invention. The preform to be produced in the injection molding tool has a neck section with an external thread and, as a rule, a neck ring in the area of the later neck of the bottle. Both the thread and the neck ring form undercuts in the shaping tool, so that the injection mold must be designed in several parts, at least in the neck area, in order to enable demoulding of the preform. The injection mold part forming the outer contour of the bottle thread and the neck ring is generally made in two parts, each of the two parts being referred to as a neck block and each part being a 180 ° peripheral portion of the thread.

However, the two-part neck jaw solution allows a slight undercut in the demolding direction, i. in the opening direction of the two-piece neck jaws, due to the thread pitch can not be avoided.

This inevitably leads to the demolding that parts of the neck jaw during demolding can come into contact with the thread ridges and can affect or damage them in an undesirable manner.

To reduce this problem, it is already common practice, the demolding stepwise, d. H. in several steps.

Recently, instead of the usual PCO 1810 thread, more and more frequently PCO 1881 threads are used, since these allow a weight saving due to their smaller design. For example, a PET preform with PCO 1881 thread is about 1.4g lighter than a PET preform with a PCO 1810 thread.

However, the undercut in the PCO 1881 threads, which results from the helical shape of the thread ridges, is even more pronounced, so that demoulding is made more difficult. In general, the larger the pitch of the thread, the greater the undercut.

In addition, the neck jaws of the mold to produce these threads are difficult to produce, since the corresponding, to be introduced into the neck jaw grooves also have an undercut, so that, for example, erosion process with undercut must be used to produce these neck cheeks.

Both the PCO 1810 thread and the PCO 1881 thread are often made with four degassing channels, i. H. the helically extending around the neck thread ridges have recesses. These degassing channels are needed if carbonated liquids are to be stored in the finished final container. When the closure cap is opened, gas formed above the liquid level, which is under high pressure, can then escape from the thread through the degassing channels even before the closure cap has been completely loosened.

These degassing channels are formed such that the flank surfaces of the thread ridges adjoining the recesses form an opening angle of 58 to 60 °. In this case, the recesses are arranged such that all lying in the direction of the thread axis threaded rests have mutually aligned recesses. Thereby, a degassing channel is formed, which has a width of about 1.82 mm in the known PCO threads, wherein the channel widens in the radially outward direction due to the opening angle of the flank surfaces. The provision of four degassing channels with opening angles of about 58 ° has proven itself in principle. Nevertheless, when filled with carbonated liquids containers when opening the bottle to an abrupt escape of the gas formed above the liquid level, which often leak liquid components involuntarily.

In this application, the information refers to "in the radial direction" or "axial direction" the thread axis or the axis of the hollow cylindrical part.

Based on the described prior art, it is an object of the present invention to provide a container of the type mentioned, which reduces the risk of abrupt escape at least in some cases and can be removed from two or multi-part neck jaws, the problem of undercut at least reduced becomes.

According to the invention, this object is achieved in that the threaded web extending around the neck portion has at least one recess or interruption, which is configured such that the threaded web has two flank surfaces delimiting the recess or the interruption on its sides facing the recess or the interruption wherein the first and second flank surfaces include an opening angle greater than 120 °.

In the case of the PCO threads described at the beginning, the thread ridges in the region of the four degassing channels are interrupted, ie. H. the hollow cylindrical neck portion has no thread ridge in this area.

Due to the inventively provided large opening angle increases when the width and height of the degassing is kept constant, the channel cross-section. In general, however, no larger channel cross-section is necessary, so that either the channel width or the channel height can be reduced due to the inventively large opening angle. In the latter case, this means that in the region of the degassing channels, the threaded ridge is not completely removed, but is reduced only in this area in the radial direction in height, so that the threaded ridge has no interruption, but only a recess.

Regardless of whether the thread ridges are interrupted or only have a recess, flank surfaces are formed by the recess or interruption on the threaded ridge, which limit the recess or interruption. These flank surfaces have an opening angle of only 58 ° in the known PCO threads. As a result of the large opening angle according to the invention, the number of degassing channels can generally be reduced. Usually only two, in some cases even only one degassing channel are necessary.

The large opening angle also has the advantage that the problem of undercut during demoulding is reduced. For this purpose, the necessary for the preparation of the thread neck jaws are formed such that the degassing channel is located at the parting plane of the two neck jaws, so that the one flank surface is formed by the one neck jaw and the other flank surface of the other neck jaw. The area in which it can come to undesirable touch, has been reduced by the large opening angle.

The undercut can even be completely eliminated when the opening angle is about 180 ° or more.

In a particularly preferred embodiment, the aperture angle is less than 200 °, and most preferably less than 185 °. It has been shown that values between 178º and 183º and best of all exactly 181º give the best results.

Basically, an opening angle of less than 180 ° again leads to a slight undercut, so that the problem mentioned at the beginning reappears. However, at only slightly smaller angles than 180 ° this problem is negligible due to the elasticity of the products to be manufactured by injection molding, so that the effect according to the invention is also achieved at opening angles which are slightly smaller than 180 °. Of course, significantly larger opening angles than 180 ° can be used. It should be noted, however, that the larger the opening angle is chosen, the wider the degassing and the stronger the thread is weakened. Depending on the material used and the thread geometry used, a too large opening angle can impair the stability of the thread ridges and thus the reliable closing function of the thread. With an opening angle of 181 degrees, the entire threaded head is only 0.05 grams lighter than the known PCO 1881 thread. The stability of the thread is therefore not affected at this opening angle.

In a further preferred embodiment, the threaded ridge on at least two recesses or interruptions, wherein the at least two recesses or interruptions in the direction of the threaded axis are aligned, so that the first flank surfaces of the first and the at least one further recess or interruption lie in a plane and the second flank surfaces of the first and the at least one further recess or interruption lie in a plane. In other words, the thread ridge, when it winds more than 360 ° around the neck portion, has a plurality of recesses or breaks spaced apart in the direction of the thread axis, all of which then provide for undercut-free removal of the thread rims.

In principle, the effect according to the invention is at least partially achieved by the provision of a single recess or interruption of the thread ridge. However, when the threaded ridge winds around more than 360 ° around the hollow cylindrical element, it is advantageous if the threaded ridge has at all in the axial direction of the recess or interruption positions further recesses or interruptions, so that in the axial direction of a continuous Degassing channel forms.

There are also multi-turn threads in which more than one threaded ridge extends helically around the neck portion. In this case, all thread ridges should have at least one recess or interruption and the recess or interruption in the axial direction are aligned. Only then a running in the thread axis direction degassing channel is formed, which then at the same time ensures due to its special shape for easy demolding.

Even if a single degassing duct designed according to the invention already provides for a simplification of demoulding, it is nevertheless provided in a preferred embodiment that the at least one threaded ridge has a second recess or interruption which is arranged diametrically opposite the first recess or interruption. In the same way, it is advantageous if the thread ridges have two groups of the aligned in the axial direction recesses or interruptions, wherein the groups are arranged diametrically opposite each other.

In other words, two degassing channels formed according to the invention, which are formed by recesses or interruptions with the indicated opening angles, are arranged on opposite sides. This ensures that can be removed in one step without the risk that the neck jaw touches a threaded ridge during removal. In addition, the corresponding neck jaws for the production of this thread can be made much easier, as they have no undercut anymore.

The present invention further relates to a multi-part mold for injection molding for producing a container with the inventively embodied degassing. According to the invention, the molding tool has two neck cheeks whose inner contours correspond to the outer contour of the neck portion of the container to be produced, wherein the neck cheeks are formed such that the first neck cheek has a surface corresponding to the first flank face of the recess or interruption and the second neck cheek has one to the Having the second flank surface of the recess or interruption corresponding surface.

The surfaces of the two neck cheeks corresponding to the flank surfaces are best arranged in the removal direction.

Further advantages, features and applications of the present invention will become apparent from the following description of a preferred embodiment and the accompanying figures. Show it:

1 a perspective view of a neck portion with an external thread according to the prior art,

2 a partial sectional view through the thread profile of in 1 shown embodiment of the prior art,

3 a perspective view of a neck portion with inventive thread,

4 a cross-sectional view through the neck portion of the embodiment of 3 .

5 a cross-sectional view through the neck portion of a second embodiment of the invention,

6a and 6b a top view and a perspective view of a third embodiment of the invention and

7a and 7b a plan view and a perspective view of a fourth embodiment of the invention.

In 1 is a perspective view of a neck portion 1 shown with a thread that essentially corresponds to the known PCO 1881 thread. The neck section 1 has a hollow cylindrical element 2 on, on the outside of a circumferential retaining ring 5 and two helical around the hollow cylindrical member 2 running thread ridges 3 . 3 ' . 3 '' . 4 . 4 ' . 4 '' are located. The first thread ridge 3 . 3 ' . 3 '' is substantially parallel to the second thread ridge 4 . 4 ' . 4 '' , Evident are two degassing channels, one of which with the reference number 6 is designated. These degassing channels interrupt the thread ridges in order to form a substantially in the direction of the threaded axis, ie axially extending degassing. These channels 6 divide the first thread ridge into the thread ridge sections 3 . 3 ' and 3 '' and divide the second threaded ridge into the threaded ridge sections 4 . 4 ' and 4 '' , Through the degassing channel 6 Form at the thread-bar sections 3 and 3 ' corresponding, the degassing channel facing flank surfaces 7 . 8th out. In the same way form at the degassing 6 facing sides of the threaded ridge sections 4 and 4 ' flank surfaces 9 . 10 out. The flank surface 7 and 8th such as 9 and 10 have an opening angle of 58 ° in the known threads. In this case, the opening angle of the angle, which includes a plane in which the one flank surface lies, with a plane in which the other flank surface lies.

In 2 is a partial cross-sectional view through the thread profile of 1 shown. It can be seen that due to the helical spiraling results in a minimal undercut, in the figure with the reference number 11 is marked. For the PCO1881 thread, the undercut size is only 0.039 mm. However, the undercut is found on each thread and on both sides of the thread. Despite the very low value, however, this leads to the fact that when demolding the threads formed in the neck jaws collide with the thread ridges. This can lead to a rotation of the container (generated by the forced removal of the undercut) and a subsequent tapping of the thread flanks on the steel edges of the neck ring. This is also called a "key pull".

In 3 an Ausführungsrom invention is shown in perspective view. Again, only the neck section 31 shown, it being understood that the rest of the container is connected downwardly, but not shown for simplicity of description. The neck section 31 also consists of a hollow cylindrical section 32 a holding section 35 surrounds. Also this thread is with two thread ridges 33 . 33 ' such as 34 . 34 ' Mistake. The degassing channel 36 However, it is much larger here. However, the enlargement of the degassing is carried out only by the fact that through the degassing 36 forming flank surfaces 37 . 38 of the first thread ridge 33 . 33 ' as well as the flank surfaces 39 . 40 of the second thread ridge 34 . 34 ' are formed with an opening angle of 180 °. In order to ensure easy demolding, the corresponding neck jaw is formed such that the dividing line of the two neck jaws in the region of the degassing 36 comes to rest, allowing the demolding parallel to the flank surfaces 37 - 40 can be done.

In 4 is a cross-sectional view of the neck portion 31 shown. It can be seen clearly that the two flank surfaces 37 . 38 , which adjoin the recess or interruption, have an opening angle α of 180 °.

In 5 is one to 4 corresponding view of an alternative embodiment shown. Here, the opening angle α, that of the flank surfaces 37 and 38 is included, 200 °.

In the 6a and 6b is a top view of an inventive thread and a perspective view of a third embodiment of the invention shown. The recess here has a depth which is greater than the height of the threaded ridge, so that the recess continues into the thread root.

In the 7a and 7b is a plan view from above and a perspective view of a fourth embodiment of the invention shown. One recognizes that here by the flank surfaces 37 and 38 limited recess does not extend to the groove bottom.

The inventive design of the degassing channel as its arrangement in the mold, the mold can be made much easier. In addition, the Entformungsvorgang can be simplified, since no consideration must be taken to the minimum undercut, as are known in the art. In addition, thread damage during removal from the mold by eliminating undercuts is reduced or even eliminated.

LIST OF REFERENCE NUMBERS

1

 neck section

2

 hollow cylindrical element

3, 3 ', 3' '

 thread web

4, 4 ', 4' '

 thread web

5

 retaining ring

6

 degassing

9, 10

 flank surfaces

11

 undercut

31

 neck section

33, 33 '

 thread web

34, 34 '

thread web

35

 holding section

36

 degassing

37, 38

 flank surfaces

39, 40

 flank surfaces

α

 opening angle

Claims (10)

Container with a hollow cylindrical neck portion ( 1 ) with external thread for receiving a closure lid, wherein the external thread at least one helically around the neck portion ( 1 ) extending threaded ridge ( 3 . 3 ' . 3 '' ), wherein the threaded ridge ( 3 . 3 ' . 3 '' ) has at least one recess or an interruption, characterized in that the recess or the interruption are designed in such a way that the threaded bar ( 3 . 3 ' . 3 '' ) at its the recess or the interruption facing sides of the recess or the interruption limiting flank surfaces ( 37 . 38 ), wherein the first and the second flank surface ( 37 . 38 ) include an opening angle that is greater than 120 °. Container according to claim 1, characterized in that the opening angle is greater than 150 ° and less than 225 °, preferably less than 190 °, more preferably between 178 ° and 182 ° and is best 180 °. Container according to claim 1 or 2, characterized in that the threaded ridge ( 3 . 4 ) at least two recesses or interruptions, wherein the at least two recesses or interruptions in the direction of the threaded axis are aligned with each other, so that the first flank surfaces ( 37 . 39 ) of the first and the at least one further recess or interruption lie in one plane and the second flank surfaces ( 38 . 40 ) of the first and the at least one further recess or interruption lie in one plane. Container according to one of claims 1 to 3, characterized in that the external thread is more continuous, so that more than one threaded ridge ( 3 . 3 ' . 3 '' ) extends helically around the neck portion, wherein all thread ridges ( 3 . 3 ' . 3 '' ) have at least one recess or interruption and the recesses or interruptions are aligned with each other in the axial direction. Container according to one of claims 1 to 4, characterized in that the at least one threaded ridge ( 3 . 3 ' . 3 '' ) has a second recess or interruption, which is arranged diametrically opposite the first recess or interruption. Container according to claim 5, characterized in that the thread ridges ( 3 . 3 ' . 3 '' ) have two groups of axially aligned recesses or interruptions, wherein the two groups are arranged diametrically opposite each other. Container according to one of claims 1 to 6, characterized in that the container is produced by injection molding. Container according to claim 7, characterized in that the container is a preform. Multi-part mold for injection molding for producing a container with a hollow cylindrical neck portion ( 1 ) with external thread for receiving a closure lid, wherein the external thread at least one helically around the neck portion ( 1 ) extending threaded ridge ( 3 . 3 ' . 3 '' ), wherein the threaded ridge ( 3 . 3 ' . 3 '' ) has at least one recess or an interruption, characterized in that the molding tool has two neck cheeks whose inner contours to the outer contour of the neck portion ( 31 ) correspond to the container to be produced, wherein the neck jaws are formed such that the first neck jaw one to the first flank surface ( 37 . 39 ) has the recess or interruption corresponding surface and the second neck jaw one to the second flank surface ( 38 . 40 ) has the recess or interruption corresponding surface. Molding tool according to claim 9, characterized in that the flank surfaces ( 37 . 38 ) correspond surfaces of the two neck jaws are arranged in Entformungsrichtung.

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